Magnetic shield for integrated circuit packaging

ABSTRACT

Structures and methods for providing magnetic shielding for integrated circuits are disclosed. The shielding comprises a foil or sheet of magnetically permeable material applied to an outer surface of a molded (e.g., epoxy) integrated circuit package. The foil can be held in place by adhesive or by mechanical means. The thickness of the shielding can be tailored to a customer&#39;s specific needs, and can be applied after all high temperature processing, such that a degaussed shield can be provided despite use of strong magnetic fields during high temperature processing, which fields are employed to maintain pinned magnetic layers within the integrated circuit.

FIELD OF THE INVENTION

[0001] The present invention relates to magnetic shielding forintegrated circuits and, more particularly, to magnetic shielding forintegrated circuits having magnetic materials used therein for whichprotection from stray external magnetic fields is desired.

BACKGROUND OF THE INVENTION

[0002] Magnetic materials are used, for example, in magnetic cellmemories and magnetic field sensors. In random access magnetoresistivememories, data is stored by applying magnetic fields and thereby causinga magnetic material in a cell to be magnetized into either of twopossible memory states. The information stored in the memory iscontained in the orientations of the magnetization vectors of themagnetic material layers used in each memory cell. Such memory cellsexhibit a pronounced decrease in electrical resistance when an appliedmagnetic field brings the magnetization vectors in different layers intoalignment. Recalling data is accomplished by sensing resistance changesin the cell. The cells can be written or erased by applying magneticfields created by passing currents through conducting lines external tothe magnetic structures, or through the magnetic structures themselves.

[0003] There are often undesirable magnetic fields in and about thedevice, which are generated either as part of the device operation orfrom external sources. Such fields can have significant effects on themagnetization of the magnetic thin film. The field can contribute to aloss of information or to storage of erroneous information in themagnetic memory cells. Thus, magnetic memory cells function best whenthey are protected from external magnetic field disturbances.

[0004] A metal with a relatively high magnetic permeability can be usedto form a shield for protection from magnetic fields. Metals that areused widely in magnetic shielding include soft magnetic or highpermeability materials, such as NiFe, NiFeMo and NiFeCu. Such magneticshielding materials, are generally available from metal supplycompanies, such as Carpenter Technology Corporation of Wyomissing, Pa.

[0005] U.S. Pat. No. 5,939,772 entitled “Shielded Package For MagneticDevices,” issued Aug. 17, 1999, describes the use of magneticallypermeable metal shields attached to the outside of a hermetically sealedceramic package. The shields are electrically connected to the packageground plane. Laminated magnetic shielding for ceramic packages is alsodescribed in U.S. Pat. No. 5,561,265, issued Oct. 1, 1996.

[0006] Ceramic package technology can be expensive. Furthermore, asperformance increases, the physical characteristics of ceramic packagesmay become limiting. Specifically, a ceramic material based on Al₂O₃ hasa relatively high dielectric constant (ε_(r)˜7-8). Additionally, becauseof the high-temperature processing, metallization is limited torefractory metals that are quite resistive, such as Mo and W.

[0007] Other references include application of magnetic shielding withina plastic package. U.S. Pat. No. 4,953,002, issued Aug. 28, 1990, forexample, teaches magnetic shielding internal to a plastic encapsulatedpackage.

[0008] Magnetic integrated circuit structures must also be housed in away that minimizes cost if they are to be viable for the commercialmemory market. Therefore, a shielding arrangement to protect magneticfilms in magnetic integrated circuit structures from significantexternal adverse influences, including external magnetic fields, andwhich can be provided economically, would be desirable. Desirably, sucha shielding arrangement should be flexible enough to meet the variedneeds of integrated circuit users.

SUMMARY OF THE INVENTION

[0009] In accordance with one aspect of the invention, a housing isprovided for protecting an integrated circuit device. The housingcomprises a molded body that encapsulates the integrated circuit device.At least one magnetically permeable foil is applied to an outer surfaceof the molded body.

[0010] In accordance with another aspect of the invention, a method isprovided for magnetically shielding a semiconductor die. The methodincludes forming a molded housing around the semiconductor die. A filmof magnetic shield material is applied to at least one outer surface ofthe molded housing. The film is applied in a manner that such that it isapproximately parallel to a major surface of the semiconductor die.Advantageously, the shield material can be degaussed just prior toapplication, after the package is subjected to high temperatureprocessing.

[0011] In accordance with another aspect of the invention, an integratedcircuit package is provided. The package includes an integrated circuitdie, a molded body encapsulating the die, and a magnetic shield layerextending parallel to a major surface of the die over an outer surfaceof the molded body.

[0012] In accordance with still another aspect of the present invention,a method is provided for packaging an integrated circuit chip. Themethod includes mounting the chip on a die carrier. Epoxy is molded overthe chip to form an encapsulant. A magnetic shield layer is thenselected for a particular integrated circuit environment. This selectedmagnetic shield is applied over the encapsulant.

[0013] In accordance with still another aspect of the invention, anintegrated circuit package is provided with an encapsulant surroundingan integrated circuit die. The encapsulant includes a recess on an outersurface thereof. The recess is configured for receiving and mechanicallyretaining a magnetic shield foil. In the illustrated embodiment, therecess includes overhanging tabs for removably trapping the foil withinthe recess.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a schematic cross section of a packaged integratedcircuit with magnetic shielding attached to outer surfaces of thepackage, according to an illustrated embodiment of the invention.

[0015]FIG. 2 is a schematic cross section of an integrated circuitencapsulated in a ball-grid array package that has magnetic shieldingattached to an outer surface of the package, according to an illustratedembodiment of the invention.

[0016]FIG. 3 is a schematic cross section of a packaged integratedcircuit with magnetic shielding set into recesses on outer surfaces ofthe package, according to an illustrated embodiment of the invention.

[0017]FIG. 4 is a perspective view of a ball-grid array package showinga recess in the top surface in which a magnetic shield is heldmechanically, according to an illustrated embodiment of the invention.

[0018]FIGS. 5A and 5B are schematic cross sections cut along lines 5A-5Aand 5B-5B, respectively, of FIG. 4.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0019] Magnetic integrated circuits, such as MRAM (magnetic randomaccess memory) devices, can be sensitive to external magnetic fields.Information is stored in MRAMs specifically as a direction ofmagnetization in a magnetic material layer. If the layer is exposed toan undesirable external magnetic field, the direction of magnetizationcan inadvertently change. Such exposure to stray fields can lead tomemory erasure, accidental writing and/or reading errors.

[0020] Of course, the external environments for magnetic integratedcircuit devices are not all the same. Some devices may be located inenvironments with strong external magnetic fields, and some may belocated in environments where external magnetic fields are negligible.When magnetic shielding is incorporated inside the packaging of amagnetic device, a best guess is made as to the size and thickness ofmagnetic shielding to use. There are drawbacks to this “one size fitsall” approach. The designer may choose to provide magnetic shielding fora worst-case scenario, thereby using more magnetic material than may berequired for many applications. In this case, customers pay for moreshielding than they might need. Additionally, customers may wish to haveshielding for only some of their applications.

[0021] Perhaps more importantly, magnetic shielding should be degaussed,i.e., provided with random magnetic orientation. In order to keep theshield degaussed, the shield should be applied as late as possible inthe packaging process. This is because during any high temperaturesteps, the chip must be exposed to a controlled magnetic field to ensurethat the “pinned” or fixed magnetic layers within the chip maintaintheir desired magnetic alignment. Even soldering a package to a circuitboard can raise temperatures high enough to risk alteration of thepinned layers' magnetization. Thus, even packaging steps should beperformed under a controlled magnetic field, if possible. Unfortunately,such a field would also tend to align the magnetic shield, if present,such that it would not remain degaussed.

[0022] It would be useful to have a system of magnetic shielding formagnetic integrated circuits that can be adapted easily for individualcustomer applications, is removable for certain applications and/or canbe readily applied after all high temperature processing, particularlythose steps in which magnetic fields are applied to maintain pinnedlayers within the chip.

[0023] The aforementioned needs are satisfied by the embodiments of thepresent invention, which provide package structures and methods forproviding magnetic shielding to an integrated circuit after packaging iscomplete. Thus, the magnetic shielding can be tailored to meet thespecific needs of the customer without incurring the expense ofover-shielding or the risk of under-shielding. More importantly, theshield can be degaussed and applied after all high temperature packagingsteps. Furthermore, in certain embodiments described herein, magneticshielding is removably applied to an outside surface of an integratedcircuit package, such that it can be removed and degaussed afterpackaging and even after mounting the package without degaussing pinnedlayers in the chip.

[0024] These and other objects and advantages of the present inventionwill become more fully apparent from the following description taken inconjunction with the accompanying drawings.

[0025]FIG. 1 is a cross-sectional, schematic drawing of a package orhousing 10 for an integrated circuit device, according to an illustratedembodiment of the invention. The package comprises a magnetic integratedcircuit 12 encapsulated within a plastic or epoxy encapsulant,preferably in the form of a molded body 14. For purposes of the presentdescription a magnetic integrated circuit is defined as an integratedcircuit containing at least one magnetic thin film layer forming a partof an active device. Preferably, the molded body 14 comprises an organicmaterial, more preferably, an elastomer or an epoxy mold compound. Theskilled artisan will appreciate that the molded body 14 encapsulates thedie 12, in contrast to ceramic packages that are hermetically sealedaround a die.

[0026] The integrated circuit 12 is encapsulated onto a die carrier orsubstrate 16. Preferably, the die carrier 16 comprises electricallyconducting leads 18. Conducting wires 20 are bonded to bond pads 22 onthe integrated circuit 12 and attached to the electrically conductingleads 18 of the die carrier 16. In an alternative “flip chip”arrangement (not shown), solder bumps on the integrated circuit arebonded to the leads 18, and conducting wires 20 are not used. In theillustrated embodiment, the leads 18 extend into electrodes 24 thatprotrude from the molded body 14 and can make connections to externalcircuitry. The electrodes 24 typically extend below the molded body 14.

[0027] As will be appreciated by the skilled artisan, the features andadvantages described herein will have application to numerous molded orencapsulated integrated circuit packages, such as lead frame packages.More recently, however, die carriers comprise plastic substrates. Forsuch packages, the electrical leads 18 and electrodes 24 representconductive traces on or in a plastic substrate extending out of themolded body 14 to form contacts that eventually form connections withlarger circuits (e.g., a motherboard).

[0028] In FIG. 1, magnetically permeable foils 26, 28 are attached toboth the top and bottom outer surfaces of the molded body 14. The foils26, 28 are thus electrically insulated from the packaged circuitry andleads. Preferably, the foils comprise soft magnetic or high permeabilitymaterials, such as nickel-iron based alloys, cobalt-iron based alloys,nickel-cobalt based alloys or amorphous ferromagnetics. More preferably,the foils comprise a NiFe-based alloy, such as mu metal or permalloy.Preferably, the foil thickness is between about 1 μm and 1000 μm. Thefoils 26, 28 are held onto the approximately flat surfaces by thinlayers of adhesive 29, preferably, an epoxy-based adhesive. The foils26, 28 are arranged to be and larger than a major surface of themagnetic integrated circuit 12. In an alternative arrangement, there isa magnetically permeable foil 26 on only one outer surface.

[0029]FIG. 2 is a schematic cross section of a ball-grid array housingor package 30 for an integrated circuit device 12, according to anotherembodiment of the invention. The integrated circuit or die 12 isattached to a rigid substrate 32 with a die attach material 34,preferably epoxy or elastomer. The rigid substrate 32 containsconductive traces 36 that connect to solder balls 38 arranged in anarray on the bottom surface of the rigid substrate 32. The solder balls38 are configured to make electrical connections to external circuitry.Conductive wires 40 provide conductive paths between bond pads 42 on theintegrated circuit 12 and the conductive traces 36 on the rigidsubstrate 32. A molded body 44 encapsulates the integrated circuit 12onto the rigid substrate 32, with the solder balls 38 serving as theelectrodes that are not covered by the molded body 44 and therefore areexposed on the outside of the package 30. Preferably, the molded body 44comprises an organic material, more preferably, an elastomer or an epoxymold compound.

[0030] In FIG. 2, a magnetically permeable foil 46 is attached to anouter surface of the molded body 44, held in place by a thin layer ofadhesive 48, preferably, an epoxy-based adhesive. The molded body 44electrically insulates the foil 46 from the package circuitry.Preferably, the foils comprise “soft” magnetic or high permeabilitymaterials, such as nickel-iron based alloys cobalt-iron based alloys,nickel-cobalt based alloys or amorphous ferromagnetics. More preferably,the foils comprise NiFe-based alloys such as mu metal or permalloy.Preferably, the foil thickness is between about 1 μm and 1000 μm. Thefoil 46 is arranged to be approximately parallel to and larger than amajor surface of the magnetic integrated circuit 12.

[0031]FIG. 3 is a cross-sectional, schematic drawing of a housing orpackage 50 for an integrated circuit device 12, according to anotherembodiment of the invention. The package 50 comprises the magneticintegrated circuit 12 encapsulated within a molded body 52. Preferably,the molded body 52 comprises an organic material, more preferably, anelastomer or an epoxy mold compound.

[0032] As described above for FIG. 1, the integrated circuit 12 isencapsulated by the molded body 52 onto a die carrier 16. Preferably,the carrier 16 includes electrically conducting leads 18. Conductingwires 20 are bonded to bond pads 22 on the integrated circuit andattached to the electrically conducting leads of the die carrier 18, 16.In an alternative arrangement (not shown), solder bumps on theintegrated circuit are bonded to electrically conducting traces on aplastic substrate in a “flip chip” arrangement, and conducting wires 20are not used. The electrically conducting leads 18 extend to formelectrodes 24 that protrude from the molded body 52 and can makeconnections to external circuitry. The electrodes 24 themselves cancomprise the contacts of a lead frame, but more preferably compriseconductive traces on or in a plastic substrate.

[0033] In FIG. 3, magnetically permeable foils 54, 56 are fitted intorecesses 58, 60 in the top and bottom outer surfaces of the molded body52. Preferably, the foils comprise “soft” magnetic or highly permeablematerials as described hereinabove. The foils 54, 56 are held in placeby thin layers of adhesive 62, preferably, an epoxy-based adhesive. Thefoils 54, 56 are arranged to be approximately parallel to and largerthan a major surface of the magnetic integrated circuit 12. In anotherarrangement, there is a magnetically permeable foil 54 and recess 58 ononly one outer surface of the molded body 52.

[0034] In accordance with one arrangement, the recesses 58, 60 areetched into the encapsulant 52 after molding. Preferably, however, therecesses 58, 60 are formed in the body 52 as molded.

[0035] Another preferred embodiment for attaching a magneticallypermeable foil in a recess in the outer surface of a molded body can beunderstood with reference to FIG. 4. A finished ball-grid array type ofpackage 70 ready for the addition of magnetic shielding is shown in aperspective view in FIG. 4. Only the molded body or encapsulant 71 isshown in FIG. 4.

[0036] The top surface 72 contains a recessed region 74 over most of itsarea. The recess 74 has two parallel edges 76 whose sidewalls 78 areapproximately perpendicular to the top surface 72, as is apparent in thecross-sectional view of FIG. 5A. The remaining two parallel edges 80 ofthe recess 74 include an overhanging tab 82 at the top surface 72, whichprotrudes into the region of the recess 74, as is apparent from thecross-sectional view of FIG. 5B. The recess 74 is preferably formed,including overhanging tabs 82, during the molding process. One or moretabs 82 are preferred over a single overhanging ledge extending thelength of the edge 80, simply to facilitate removal of the mold.

[0037]FIGS. 5A and 5B show only the top outer surface portion of ahousing for an integrated circuit. It will be understood that the outersurface arrangement shown in FIGS. 5A and 5B can be used with any numberof integrated circuit and wiring arrangements consistent with moldedbody packages, including those discussed above for FIGS. 1 and 2.Additionally, the outer surface arrangement shown in FIGS. 5A and 5B canbe used either on only one package surface or on both major packagesurfaces, according to the requirements of the operating environment.Preferably, the molded body 71 comprises an organic material, morepreferably, an elastomer or an epoxy mold compound.

[0038]FIG. 5A is a cross section of the recess 74 cut through the recessedges 76 whose sidewalls 78 are approximately perpendicular to the topsurface 72 of the molded body 71. A sheet of magnetic shield material 84lies within the recess 74 with its edges 86 adjacent to the sidewalls 78of the recess 74.

[0039]FIG. 5B is a cross section of the recess 74 cut along a surfaceperpendicular to the surface shown in FIG. 5A. The top edges 80 of therecess 74 have at least one overhanging tab 82 at the top surface 72 ofthe housing 70 and, deeper inside the recess 74, sidewalls 88 that areapproximately perpendicular to the plane of the top surface 72. Theoverhanging tabs 82 protrude into the region of the recess 74. A sheetof magnetic shield material 84 is trapped within the recess 74, belowthe tabs 82, with its edges 90 adjacent to the sidewalls 88 of therecess 74. It will be understood that, in other arrangements, the tabs82 can taper to the recess floor rather than having the illustratedperpendicular sections 88. The illustrated tab configuration, taperingabove and below the innermost protrusion, facilitates deflection toinsert and/or remove the magnetic shield 84.

[0040] In the illustrated embodiment, no adhesive is used to hold thesheet of magnetic shield material 84 in place within the recess 74 ofthe molded body 71 for the magnetic integrated circuit. The sheet ofmagnetic shield material 84 is cut to fit the size of the recess 74. Thesheet 84 is placed into the recess 74 by bending the sheet 84 slightlyto fit under the overhangs 82 and then releasing the sheet 84 to fitinto place against the sidewalls 88 of the recess 74. The width of therecess opening within the overhang edges 82 is less than the width ofthe magnetic material sheet 84, thus providing a mechanical means ofkeeping the magnetic material sheet 84 in place. It will be understoodthat, if desired, adhesive can additionally be employed.

[0041] Advantageously, the magnetic shield 84 can additionally beremoved and replaced. Thus, a package can be shipped with the shield 84in place. The customer can remove the shield 84, conduct additional hightemperature processing in a strong magnetic field (without affecting theshield), and replace the shield after completion of high temperaturepackaging steps. Alternatively, after installation and use, the shield84 can be removed for degaussing again, should the need arise.

[0042] The embodiments of the invention have been described usingexamples of packages that contain one integrated circuit or die. Theembodiments of the invention are equally useful for a multi-die package,wherein integrated circuits are arranged next to one another and/orstacked one over another within one molded package. Connections amongthe dies and between the dies and conducting traces connected toelectrodes that protrude from the package can be made by wire bonding orby solder bump bonding as described above with respect to theillustrated embodiments.

[0043] The structures and methods described above in the illustratedembodiments offer many advantages for magnetic shielding of magneticintegrated circuits. Fully processed and packaged integrated circuitdevices can be removed from the fab environment and inventoried. At thispoint, all high temperature processing has been completed. Magneticshielding, tailored to meet a particular customer's requirements, can beadded to the outside of the packages just prior to shipping. Themagnetic shielding is preferably degaussed and/or given a particularmagnetic alignment according to customer needs. This would not bepossible if the magnetic shielding were introduced into the integratedcircuit or the package before all high temperature processing wascomplete. Moreover, the embodiments described herein obtain magneticshielding, post-processing tailoring and the benefits of low-dielectricepoxies and high conductivity copper metallization for IC packaging.

[0044] Although the foregoing description of the preferred embodimentsof the present invention has shown, described and pointed out thefundamental novel features of the invention, it will be understood thatvarious omissions, substitutions and changes in the form of the detailof the apparatus as illustrated as well as the uses thereof may be madeby those skilled in the art, without departing from the spirit of thepresent invention. Consequently, the scope of the present inventionshould not be limited to the foregoing discussion, but should be definedby the appended claims.

We claim:
 1. A housing for protecting an integrated circuit devicecomprising: a molded body encapsulating the integrated circuit device;and at least one magnetically permeable foil applied to an outer surfaceof the molded body.
 2. The housing of claim 1, wherein the integratedcircuit device comprises at least one magnetic thin film.
 3. The housingof claim 1, wherein the molded body comprises an organic material. 4.The housing of claim 3, wherein the organic material comprises an epoxymold compound.
 5. The housing of claim 1, wherein the molded bodyencapsulates the integrated circuit device on a plastic substrate. 6.The housing of claim 5, wherein the plastic substrate comprises a ballgrid array substrate.
 7. The housing of claim 5, wherein wire bondsextend between the device and electrically conductive traces on theplastic substrate.
 8. The housing of claim 5, wherein solder bumps onthe device are in contact with electrical traces on the plasticsubstrate.
 9. The housing of claim 1, further comprising electricalleads protruding from the molded body.
 10. The housing of claim 9,wherein the electrical leads comprise conductive traces on a plasticsubstrate.
 11. The housing of claim 1, wherein the integrated circuitdevice comprises a plurality of integrated circuit dies.
 12. The housingof claim 1, wherein the magnetically permeable foil applied to the outersurface of the molded body is approximately parallel to a major surfaceof the integrated circuit device.
 13. The housing of claim 1, furthercomprising a layer of adhesive between the outer surface of the moldedbody and the at least one magnetically permeable foil.
 14. The housingof claim 1, wherein at least one outer surface of the molded bodycomprises a recess designed to receive the magnetically permeable foil.15. The housing of claim 14, wherein the at least one outer surface ofthe molded body further comprises an overhang along at least a portionof a perimeter of the recess, the overhang providing a mechanical meansto hold the magnetically permeable foil within the recess.
 16. Thehousing of claim 15, wherein the overhang comprises at least one slopedtab protruding into the recess.
 17. The housing of claim 1, wherein themagnetically permeable foil is selected from the group consisting ofnickel-iron based alloys, cobalt-iron based alloys, nickel-cobalt basedalloys, and amorphous ferromagnetics.
 18. The housing of claim 1,wherein the magnetically permeable foil has a thickness between about 1μm and 1000 μm.
 19. A method of magnetically shielding a semiconductordie, comprising: forming a molded housing around the semiconductor die;and applying a film of magnetic shield material to at least one outersurface of the molded housing, the film being approximately parallel toa major surface of the semiconductor die.
 20. The method of claim 19,wherein forming a molded housing comprises encapsulating a plurality ofsemiconductor dies.
 21. The method of claim 19, wherein the at least oneouter surface of the molded housing comprises a recessed region, intowhich region the film of magnetic shield material is applied.
 22. Themethod of claim 21, wherein applying comprises fitting the film withinthe recessed region under an overhang along at least a portion of aperimeter of the recessed region.
 23. The method of claim 19, whereinapplying the film of magnetic shield material to at least one outersurface of the molded housing comprises applying the film to both a topouter surface and a bottom outer surface of the molded housing.
 24. Themethod of claim 19, wherein the semiconductor die is attached to aplastic substrate before the molded housing is formed, and the moldedhousing encapsulates the semiconductor die on the plastic substrate. 25.The method of claim 24, wherein the plastic substrate comprises a ballgrid array substrate.
 26. The method of claim 24, further comprisingbonding wires between the semiconductor die and electrical traces on theplastic substrate after the semiconductor die is attached to the plasticsubstrate and before forming the molded housing.
 27. The method of claim24, further comprising bonding solder bumps on the semiconductor die toelectrical traces on the plastic substrate before forming the moldedhousing.
 28. The method of claim 19, wherein applying the film ofmagnetic shield material to at least one outer surface of the moldedhousing comprises attaching the film to the molded housing with anepoxy-based adhesive.
 29. The method of claim 19, wherein the magneticshield material is selected from the group consisting of mu metal andpermalloy.
 30. The method of claim 19, wherein applying the film ofmagnetic shield material is conducted after all high temperatureprocessing.
 31. The method of claim 19, further comprising degaussingthe film of magnetic shield material before applying the film to the atleast one outer surface of the molded housing.
 32. The method of claim31, further comprising removing the film of magnetic material from theouter surface of the molded housing before degaussing and re-applyingthe film.
 33. An integrated circuit package, comprising: an integratedcircuit die; a molded body encapsulating the die; and a magnetic shieldlayer extending over an outer surface of the molded body and parallel toa major surface of the die, the magnetic shield layer being electricallyinsulated from the die.
 34. The integrated circuit package of claim 33,wherein the magnetic shield layer is mechanically trapped within amolded recess on an outer surface of the molded body.
 35. A method ofpackaging an integrated circuit chip, comprising: mounting the chip on adie carrier; molding epoxy over the chip to form an encapsulant;selecting a magnetic shield layer for a desired integrated circuitenvironment; and applying the selected magnetic shield layer over theencapsulant.
 36. The method of claim 35, further comprising forming arecess in a major surface of the encapsulant, wherein applying comprisesfitting the selected magnetic shield layer within the recess.
 37. Themethod of claim 36, further comprising removing the selected magneticshield layer from the recess, conducting high temperature processingupon the packaged chip while the magnetic shield layer is removed, andreplacing the magnetic shield layer after high temperature processing.38. The method of claim 37, further comprising applying a strongmagnetic field to the packaged chip during the high temperatureprocessing.
 39. The method of claim 35, wherein applying comprisesadhering.
 40. An integrated circuit package comprising an encapsulantsurrounding an integrated circuit die, the encapsulant including arecess on an outer surface thereof, and the recess configured forreceiving and mechanically retaining a magnetic shield foil.
 41. Theintegrated circuit package of claim 40, wherein the encapsulantcomprises overhanging tabs protruding into the recess for removablytrapping the foil within the recess.